1. Field of the Invention
The invention covers the field of conveying technology and is concerned, in particular, with conveying printed products.
2. Description of Related Art
Apparatuses in the form of paddle wheels for transferring sheet-like products are generally known. They are used, for example in printing technology, to receive folded printed products coming from a rotary printing machine, or from the folding unit thereof, and to deliver them in imbricated form onto delivery belts arranged beneath the paddle wheel. The resulting imbricated formation can then be fed for further processing.
The products are fed to the paddle wheel usually from above or from the side, with the folding edge in front, and are discharged again approximately after a half revolution of the wheel, with the assistance of gravitational force, at the lowermost point of the path. A fixed-location stripping device is usually present in order to assist this process, the stripping device acting on the leading edge (folding edge) and pushing the product out of the compartment as the wheel rotates further.
In order for a constant imbrication spacing to be produced on the delivery belt, it is desirable for the movement of the product to be well-controlled as the products exit from the paddle wheel.
In order for a regular imbrication spacing to be produced, it is known, for example from EP-A 0 739 840, EP-A 1 510 488 or WO 98/16455, for controlled grippers to grip the printed products in the lower part of the movement path, shortly before they exit from the compartments of the paddle wheel, at their edge which rests on the base of the compartments (compartment base), i.e. at the leading edge, as seen in respect of the formation of products entering the paddle wheel. The grippers here also perform the function of the aforementioned stripper. The printed products secured by the grippers are removed from the paddle-wheel compartments on account of the movement of the gripper and paddle-wheel compartment relative to one another. Since the grippers accompany the compartments, or compartment bases, some way, the products are moved, and conveyed further, at the receiving location in the direction of circulation of the paddle wheel. The products are then deposited in imbricated form from above on a removal conveyor or transferred to a further gripper conveyor. The imbricated formation produced is one in which the leading edges—as in the original formation—are arranged upstream of the trailing edges. Since the grippers only act on the products in the lower part of the movement path of the paddle wheel, there is a risk of the products sliding out of the compartments in an uncontrolled manner, on account of gravitational force, before being gripped. This can also give rise to irregularities in the formation produced.
In order for it to be possible, in the case of such apparatuses, for the grippers to act on the leading edge, which is located in the region of the compartment base, the movement path of the grippers is located well within the paddle wheel, as seen in a plan view of the axis of rotation of the paddle wheel. The products are guided out of the compartments in the downward direction and conveyed further by the gripper conveyor beneath the paddle wheel and/or deposited, with the assistance of gravitational force, on a conveying belt arranged beneath the paddle wheel. This requires the apparatus as a whole (paddle wheel and conveying belt arranged therebeneath) to be of a certain minimal overall height. As seen in a projection of the axis of rotation of the paddle wheel, the circulatory path of the grippers, and of the drive means thereof, is located, at least in part, within the surface area of the paddle wheel. The gripper conveyor has to engage in the paddle wheel, which is mechanically complex.
A further disadvantage resides in the fact that the leading edge is gripped. At the exit of a rotary printing machine, the leading edge is usually the folding edge of the product. It is precisely in the case of relatively thick or multi-part printed products, prior to stitching or stapling, that gripping of the folding edge can result in product parts falling out. Moreover, the product, for the purpose of further processing, often has to be introduced into a further-processing station with the folding edge in front, e.g. it has to be introduced into an insertion or cutting drum in order for further products to be inserted or for the edge located opposite the folding edge to be cut. In such cases, therefore, engagement around the product is necessary, and this requires transfer to a further gripper conveyor or depositing and regripping operations. The additional component which is necessary for engaging around the product renders this practice complex and expensive.
ER-A 0 265 735 discloses the practice of evening out the products, in order to produce a constant imbrication spacing, by action on their trailing edges once they have been removed from the compartments. For this purpose, a conveying belt with an auxiliary conveyor is arranged beneath the paddle wheel, and this auxiliary conveyor moves in the same direction as the direction of circulation at the receiving location. The auxiliary conveyor has a plurality of clamping elements. The products are pushed out of the compartments of the paddle wheel in the downward direction on account of gravitational force, and with the assistance of strippers acting on the leading edges, and end up located in an imbricated formation on the conveying belt. The clamping elements serve as a stop for the trailing edges of the already deposited products and clamp the same firmly against the conveying belt. They thus ensure a constant spacing of the trailing edges on the conveying belt. Once the product has been evened out in this way, the clamping elements are removed and the products are conveyed further in the evened-out imbricated formation.
As in the case in the above described apparatuses, there is the disadvantage here that the products can slide out of the compartments in an uncontrolled manner. For this reason, the known apparatus has guide elements for the products, e.g. lateral directing plates or supporting belts, which are intended to support, in particular, the trailing edges. It is, thus, not possible to prevent slipping of product parts, for example of different formats, within a product. Moreover, the conveying belt moves in the same direction as the paddle wheel in its lower region. It is, thus, also the case here that the role of the leading and trailing edges in the exiting formation remains unchanged in relation to the original formation.
It is, thus, an object of the invention to reduce the disadvantages described above. In particular, the intention is to provide a method and an apparatus which make it possible for products, in particular folded printed products, to be transferred in a well-controlled and reliable manner between a paddle wheel and a further conveying device.